IEEE-488 cables are used to interconnect programmable measurement and instrumentation devices to form an integrated system. These cables are carefully shielded to minimize interference between signal lines and reduce susceptibility to external noise, and to minimize transmission of signals to the external environment. Each cable terminates in a right angle connector having a standardized male fitting on one side and a standardized female fitting on the opposite side of the connector. These fittings are designed to enable "piggy backing" of a series of cables as described in more detail below.
The IEEE-488 cables are often used in circumstances where there are obstructions in the path of the cable. For example, a panel of a console may physically block the path of the cable. One commercially available adaptor which is designed to interconnect two IEEE-488 cables through a panel is bulkhead adaptor model number CIB24BA available from L-Com, Inc. of North Andover, Mass. The CIB24BA bulkhead adaptor contains a female fitting on one side and a male fitting on the opposite side.
Two or more IEEE-488 cables can be joined together by inserting the male fitting of the connector of a first cable into the female fitting of the connector of a second cable. Two hold down screws, one on each side of the female fitting, enable the male fitting of the first cable to be securely attached to the female fitting of the second cable. Frequently, it is desired to "piggyback" more than two IEEE-488 cables. Piggybacking refers to coupling more than two cables at a single junction. However, since the female cable fitting of the second cable must be used to connect with the male fitting of the first cable, no additional cables with female connectors can be "piggybacked" to the second cable. This is a significant drawback when the connector of the first cable is mounted on a panel of a console such that its female fitting is not accessible on the outside of the console.
Additionally, cables are traditionally connected so that the cable portions which extend from the connectors approach and leave the bulkhead adaptor from the same direction. For example, a cable approaches from right to left, terminates in a connector which is mated to one fitting of the adaptor, and the cable on the other side of the adaptor then extends away from the adaptor back toward the right on the other side of the panel. This arrangement is awkward if the second cable communicates with equipment which is located toward the left of the adaptor.